When an existing safety valve in a well becomes inoperable, operators must take measures to rectify the problem by either working over the well to install an entirely new safety valve on the tubing or deploying a safety valve within the existing tubing. In the past, operators may have simply deployed a subsurface controlled subsurface safety valve in the well. The subsurface controlled valves could be a velocity valve or Protected Bellows (PB) pressure actuated valve. However, regulatory requirements and concerns over potential blowout have prompted operators to work over the well rather than deploying such subsurface controlled valves. As expected, working over a well can be time consuming and expensive. Therefore, operators would prefer to deploy a surface controlled safety valve in the tubing of the well without having to work over the well.
Current technology primarily allows surface controlled safety valves to be deployed in wells that have either an existing tubing-mounted safety valve or a tubing-mounted safety valve landing nipple. In French Patent No. FR 2734863 to Jacob Jean-Luc, for example, a surface controlled safety valve device 100 is disclosed that can be landed in an existing landing nipple from which the original safety valve has been removed. This safety valve device 100 reproduced in FIGS. 1A-1B is set in the landing nipple 10 using a special adapter 160 that mechanically hold the locking dogs 102 and the flapper 104 of the device 100 until the device 100 can be properly positioned in the landing nipple 10. Then, when releasing the device 100, the adapter 160 must disengage from the device 100 so that the locking dogs 102 engage the nipple 10 while simultaneously letting the flapper 104 close. Moreover, these steps must be performed while not damaging a hydraulic connector 120 and intermediate tubing 130 exposed in the device 100 adjacent to where the special adapter 160 holds the device 100.
When deployed in the landing nipple 10, a conduit (not shown) communicated through the tubing connects to the device 100 to operate the flapper 104. This conduit conveys hydraulic fluid to the connector 120 connected to a fixed portion 123 in the device 100. This fixed portion 123 in turn communicates the fluid to the intermediate tubing 130 that is movable in the fixed portion 123. A cross port 132 from the intermediate tubing 130 communicates the fluid so that it fills a space 133 and moves a sleeve 134 connected to the intermediate tubing 130. As the sleeve 134 moves down against the bias of a spring, it opens the flapper 104. Because the mechanisms for operating the device 100 are exposed and involve several moving components, the mechanical operation of this device 100 is less than favorable. Moreover, the exposed mechanisms that operate the device 100 with their several moving parts can become damaged.
In U.S. Pat. No. 7,040,409 to Sangla, another safety valve device for wells is disclosed that can be deployed in tubing without the need for an existing landing nipple. This device 200 is reproduced in FIGS. 2A-2B. As shown in FIG. 2B, the lower part of the device 200 has a flapper 210 that closes by a spring (not shown) and opens by a sleeve 212 under the thrust action of a ring 214 connected to a piston 216. With sufficient hydraulic pressure in a valve opening chamber 218, the piston 216 and ring 214 press the sleeve 212 against the bias of the spring 213 so that the sleeve 212 slides down and opens the flapper 210. With the flapper 210 open, a passage 202 in the device 200 permits fluid communication through the device 200. In the absence of pressure in the chamber 218, the spring 213 pushes the sleeve 212 upwards so that the flapper 210 closes.
To position the device 200 in tubing 20, the lower part of the device 200 as shown in FIG. 2B has lower anchor dogs 220a. These lower dogs 220a are displaced radially by a lower piston 222a whose end has the shape of a cone on which the lower dogs 220a rest. The lower piston 222a is pushed under the lower dogs 220a by the hydraulic pressure in a lower anchor chamber 224a so that the displacement of the lower piston 222a locks the lower dogs 220a on the wall of tubing 20. Locks 226a, such as dog stops or teeth, hold the lower piston 222a in place even when the pressure has dropped in lower chamber 224a. The upper part of the device 200 as shown in FIG. 2A similarly has upper anchor dogs 220b, piston 222b, hydraulic chamber 224b, and locks 226b. 
To create a seal in the tubing 20, the device 200 uses a pile of eight cups 230 that position between the device 200 and the tubing 20. These cups 230 have a general herringbone U or V shape and are symmetrically arranged along the device's central axis. Hydraulic pressure present in a sealing assembly chamber 234 displaces a piston 232 that activates the cups 230 against the tubing 20. Locks 236 hold this piston 232 in place even without pressure in the chamber 234.
Hydraulic pressure communicated from the surface operates the device 200. In particular, rods (not shown) from the surface connect to a connector 240 that communicates with internal line 242. This internal line 242 communicates with an interconnecting tube 250 to distribute hydraulic pressure to the valve opening chamber 234 via a cross port 243, to the anchor chamber 224a-b via cross ports 244a-b, and to the sealing assembly chamber 218 via the tube 250. A hydraulic pressure rise in line 242 transmits the pressure to all these chambers simultaneously. When the hydraulic pressure drops in line 242, the device 200 closes but remains in position, anchored and sealed. A special profile 204 arranged at the top of the device 200 can be used to unanchor the device 200 by traction and jarring with a fishing tool suited to this profile 202. By jarring on the device 200, a series of shear pins are broken, thus releasing anchor pistons 222a-b and the sealing piston 232. The released device 200 can then be pulled up to the surface.
As with the valve 100 of FIGS. 1A-1B, the valve 200 of FIGS. 2A-2B also has features that are less than ideal. First, the pile of cups 230 offers less than desirable performance to hold the device 200 in tubing 20. In addition, the intricate arrangement and number of components including line 242; cross ports 243 and 244a-b; tube 250; multiple chambers 218, 224a-b, and 234; multiple pistons 216, 222a-b, and 232; and exposed rod 216 make the device 200 prone to potential damage and malfunction and further make manufacture and assembly of the device 200 difficult and costly. Accordingly, a need exists for more effective subsurface safety valves that can be deployed in a well.